Do my Batt's need charging?

[MmatsDude 10+ year member]

Sup guys got a new hc1800 on the front and pmd3100 on the trunk, both of them sit at around 12.4 volts, when i turn on the car my kinetik stays @ 12.6 volts and my pm stays @ 12.7 or 12.8 volts @ idle when i rev it up a little bit the voltage goes up too 13.8, if i rev it up a little harder it goes over 14 volts, but i think i should be getting more @ idle though since i have an EA 180 amp alernator, this is without the amps connected yet.

i did a second test, i left the AC on and all the lights on for 5 minutes while the car was off, when i turned the car on the voltage was reading the same 12.6 and 12.8volts and the amperage was in between 40 and 50 amps, i then gave it a good rev, and the front batt pulled over 100 amps @ 13.7 volts, i guess it was charging it self back from everything being on when the car was of, the pm on the back read the same volts except it pulled less amperage.

i also have 7 grounds on my big3 so i know the grounds are not the problem lol and im runnin neg wire from batt to batt all the way from the front batt to rear can i also ground the rear batt to chassis(trunk batt) to get an even better ground? eventhough im runnin neg wire from batt to batt?

idk if this is normal but i think i should be getting more voltage @ idle

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[mazzasec 5,000+ posts]

Maybe its your alt? If I am correct if your car is on and literally no music playing you should be idling at 14.4 unless you just got a shitload of batteries

 

[helotaxi 5,000+ posts]

Sounds to me like the batteries are fine but your alt is not. With no load at idle your voltage should be over 12.6V. That isn't even enough to charge the batts.

 

[MmatsDude 10+ year member]

hopefully nothings wrong with the alt //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif ill see what happens when i hook everything up

 

[king ranch 5,000+ posts]

shit mine rest at 12.7 after being not charged for like 1 week when the truck is running they are above 14

 

[fbi90909 5,000+ posts]

what car do you have?

 

[MmatsDude 10+ year member]

what car do you have?

toyota celica st 97 coupe

 

[snb778 5,000+ posts]

in order to get higher voltage at idle... your alternator had to be built properly...as in the pulley should be smaller than stock, and the diodes should be changed, and something else... don't remember... but 12.6 is low for any car

disconnect your wires runnin to the system from the batt, and see what happens

 

[MmatsDude 10+ year member]

in order to get higher voltage at idle... your alternator had to be built properly...as in the pulley should be smaller than stock, and the diodes should be changed, and something else... don't remember... but 12.6 is low for any car
disconnect your wires runnin to the system from the batt, and see what happens

well the pulley is the same size and what are the diodes? yeah but when i rev it just a little bit the voltage dramatically increases to 13.5 and over.//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[tommyk90 5,000+ posts]

Sounds to me like the alternator doesn't have any output at idle. Only two ways to fix that.

1) Get a smaller pulley so the alt spins faster at the idle RPM

or

2) Set your idle RPM higher.

 

[MmatsDude 10+ year member]

Sounds to me like the alternator doesn't have any output at idle. Only two ways to fix that.
1) Get a smaller pulley so the alt spins faster at the idle RPM

or

2) Set your idle RPM higher.

1) were can the pulley be replace? and how much would that cost?

2) how do i do that?

 

[audiolife 5,000+ posts]

i would also get a charger or get them charged with an agm charger. they should beable to rest at at least 12.7 v. my 1400 rested at 12.9 with a stock voltage (14.2) going to it now it rests at 13v with a 14.6v charge from the alt.

Doesn't sound like your alt is working right for sure though

 

[helotaxi 5,000+ posts]

The alt should charge the battery at idle as delivered from the factory. If it doesn't there is something wrong with it. Voltage should not change with RPM in a no-load situation. If it does there is something wrong with the alt.

 

[Saint211 10+ year member]

Definitely sounds like an alternator problem IMHO.

At idle you should have higher voltage. I have a stock alternator, a deka 9A34M up front, and a deka 9A31 in the rear right now. Big three is done in 0 gauge and I also have three power runs fused @ 250 amps a run, and 2 straight ground runs for now Im pretty sure the batts rest at 12.6 car off. At idle I charge at 14.5 after sitting all night on a chilly morning... that settles to 14.2 after warming up.

If Im warmed up driving and wang for half an hour then park and idle it(only 2800 watts for the time being) I charge at 13.9-14.1

Point is I idle at 13.9-14.5 with a stock 130 amp alternator. Your setup is technically "beefier" than mine right now with the exception that I have multiple runs between batts. You said your batts rest at 12.4. Then you said your car idles in the 12's..... and you get into the 13's revving the engine. You are pretty much running off the batts at low RPM's. this could be a number of problems... im not an alternator expert but it sounds like you either need a different size pulley

or a different alternator. I have talked to nathan and he says he builds all custom alts, but this could also be a problem you would see from an alternator that is re-wound too much.

By the way all of my general numbers come from the voltage meter on my pioneer, as well as DMM tests done by myself at each battery and each amp. The rear of the car is generally very close to the front, as my power run to the back is super beefy for only 2800 watts.

Somethings just not right there man. Try talking to nate, I know he mentioned to me about the pulleys, so that might be a good place to start

 

[helotaxi 5,000+ posts]

It could also be the regulator going out.